The objective of this research is to determine the effect in animals of widely used psychotropic drugs which, upon interaction with nitrites (of environmental, dietary or salivary origin), yield potentially carcinogenic nitrosamines. The information sought should help the clinician in considering the risk versus benefits obtained from each drug and in adopting safer therapeutic alternatives. A first group of psychotropic drugs containing secondary or cyclic amines have been nitrosated in vitro, and the corresponding nitrosamino derivatives have been obtained in high yield. These nitrosamines will be administered to newborn, adult and pregnant animals. In a parallel experiment the drugs containing secondary or cyclic amines will be administered with nitrites to the same types of animals. In both experiments the possible tumor incidence in each group will be determined. Appropriate control groups will be maintained in each case. We have studied, in vitro, the dealkylating nitrosation upon interaction with nitrites of a second group of psychotropic drugs containing tertiary amines. In these experiments variable amounts of the potent carcinogen dimethylnitrosamine have been formed in conditions similar to those found in the stomach. These in vitro data are the basis for the in vivo carcinogenicity studies in which pregnant animals have been administered, at subtoxic levels, a psychotropic drug containing a tertiary amine and nitrites. In this manner the transplacental transfer and possible tumor incidence in the offspring as compared with the controls will be determined.